Project Summary/Abstract This proposal for a five-year mentored research career development project focuses on elucidating the role of the type 1 diabetes (T1D) PTPN2 risk allele in loss of B cell anergy. Previously B cells bearing antigen receptors with high affinity for insulin were found only in the anergic B cell compartment of healthy individuals. Importantly, these cells leave this compartment in a proportion of first-degree relatives (FDRs), and in all autoantibody positive pre-diabetics and recent onset diabetics. Departure of these autoreactive anergic B cells in FDRs was shown to be associated with high risk T1D HLA alleles, and three high risk non-HLA alleles, including INS (rs689), PTPN2 (rs1893217), and IKZF3 (rs2872507). Of the three non-HLA risk alleles, only PTPN2 has been previously shown to be a negative regulator of signaling. However these previous studies were completed in mice, not humans, and their exact mechanism by which they contribute to development and signaling has yet to be determined. This application proposes to determine the effect of the T1D risk variant of PTPN2 in maintenance of B cell anergy. Aim 1 will explore the effect of the risk variant on the phenotype of the B cell compartment in FDRs of T1D patients and their response to stimulation. Aim 2 will explore the relationship of loss of anergic B cells with the high risk T1D genotype allele, Ptpn2, using a reductionist mouse model. The potential impact of these studies will lie in understanding how risk alleles conspire to undermine maintenance of immune tolerance to autoantigens in T1D. The candidate is an Instructor at the Barbara Davis Center for Diabetes and has brought together a diverse team of experts to serve on her advisory committee. The outlined proposal builds upon the candidate's previous research but will enable advancement of technical and analytical skills utilizing state-of-the-art technologies and will allow pursuit of new avenues of B cell research. In addition, the training and development plan is comprehensive and tailored to her needs, which will enable her to transition to independence as a highly productive veterinary scientist in the field of autoimmunity.